1. Field of the Invention
The present invention relates to a head slider for a disk drive.
2. Description of the Related Art
In recent years, a reduction in size and an increase in capacity of a magnetic disk drive as a kind of external storage device for a computer have been desired. One method of increasing the capacity of the magnetic disk drive is to increase the number of magnetic disks mounted on a spindle, and in association therewith the spacing between the magnetic disks in a recent magnetic disk drive has increasingly been reduced. In a recent magnetic disk drive, a flying type magnetic head slider adopting a contact start and stop (CSS) system has frequently been used. In such a flying type magnetic head slider adopting the CSS system, the magnetic head slider comes to contact with a magnetic disk when the disk drive stops operation, whereas the magnetic head slider is kept flying at a microscopic height from the disk surface by an air flow produced over the disk surface rotating at a high speed in recording or reproducing information.
In the flying type magnetic head slider adopting the CSS system, an electromagnetic transducer (magnetic head element) is built in the slider for receiving the air flow produced over the disk surface, and the slider is supported by a suspension. Accordingly, when the magnetic disk remains still, the slider including the electromagnetic transducer is in contact with the disk surface, whereas when the magnetic disk is rotated, a disk opposing surface of the slider opposed to the magnetic disk receives an air flow generated by rotation of the magnetic disk, and the slider flies from the disk surface. The electromagnetic transducer built in the slider is moved over the disk surface as being supported by the suspension to perform recording or reproduction of information at a given track.
In a magnetic disk drive employing a conventional flying type magnetic head slider, a pair of rails are provided on opposite side portions of a disk opposing surface of the magnetic head slider opposed to the disk surface. Each rail has a flat air bearing surface. Further, a tapering surface is formed on each rail so as to meet an air inlet end surface of the slider. The air bearing surface of each rail receives an air flow generated by high-speed rotation of a magnetic disk to fly the slider and stably maintains a microscopic distance between the disk surface and the electromagnetic transducer.
According to the CSS system, a high flying stability and a microscopic flying height (submicrons) can be ensured. However, when the disk remains still, rail surfaces (air bearing surfaces) of the slider are in contact with the disk. Accordingly, when the magnetic disk drive starts or stops operation, the air bearing surfaces relatively slides on the disk. To cope with such sliding, a protective film made of a hard material such as carbon and a lubricating layer for reducing friction and wear of the protective film to improve durability of the magnetic disk are formed on a recording layer of the disk. Owing to the presence of the lubricating layer, friction and wear of the protective film can be reduced. However, when the disk drive stops operation, there is a possibility that stiction between the disk and the slider may occur to cause a problem that the disk drive cannot be restarted.
To prevent the stiction between the disk and the head slider, there has been proposed a technique of reducing the contact area between the head slider and the disk surface by providing a plurality of pads (projections) on the flying surface (air bearing surface) of the head slider (e.g., Japanese Patent Laid-open No. 8-69674). Each pad for preventing the stiction in the prior art has a cylindrical shape uniform in diameter from the top to the bottom, and it is formed at right angles to the air bearing surface of the head slider. As another conventional head slider, each pad for preventing the stiction is formed on a step surface lower in level than the air bearing surface. In this case, the height of each pad from the step surface is set slightly larger than the height of the air bearing surface.
The diameter of each pad is set greater than or equal to a certain diameter in consideration of wearing of each pad and less than or equal to a certain diameter in consideration of a coefficient of friction. In considering a stiction margin, a higher pad is required. However, the height of each pad cannot be set larger than or equal to a certain height in consideration of a flying attitude of the head slider such that the position of the magnetic transducer becomes a lowest point of the head slider in its flying condition. In the case that each pad becomes closer to the disk surface than the magnetic transducer in the flying condition of the head slider, a spacing loss is produced to impair the performance of the disk drive. If the height of each pad is excessive, there is a possibility that each pad may come into contact with the disk surface to cause head crash. Thus, the height of each pad is limited, so that there arises a problem that the stiction between the head slider and the magnetic disk due to an initial error occurring in assembling or transporting the disk drive, causing the impairment of the reliability of the disk drive.